For example, a conventional filtration filter device is disclosed in Patent Document 1 (identified below), which is known as a type of filtration filter device.
The filtration filter device in Patent Document 1 includes a filtration filter that filters an object contained in a fluid, and a housing member that has an interior space in which the filtration filter is disposed. The housing member includes an inflow-side projecting portion via which the fluid flows into the interior space and an outflow-side projecting portion via which the fluid that has passed through the filtration filter flows out from the interior space.    Patent Document 1: Japanese Unexamined Patent Application Publication No. 2007-304016.
However, from perspective of observation of the object filtered and left on the filtration filter, the existing filtration filter device as disclosed in Patent Document 1 leaves room for improvement.